Fig. 1

Sketch map of the Changjiang Estuary. The green dot in the figure indicates the position of Chongming Dongtan (eastern shoal) meteorological station; black dots indicate the water intakes of reservoirs"

Fig. 2

Shorelines of the Changjiang Estuary in 2007 and 2021. The black dots in the figure represent the measuring stations; the red dots represent the model output points in the North Branch; the red lines divide the North Branch into four areas. S1 and S2 are the transects of the upper and lower reaches of the North Branch; S3 and S4 are the transects of the middle and upper reaches of the North Channel; S5 is the transect in the Hengsha Channel"

Tab. 1

Changes in channel surface area in various regions of the North Branch of the Changjiang Estuary (unit: m2)"

Fig. 3

Changes in the depth of the Changjiang Estuary from 2007 to 2021. Red indicates deposition; blue indicates erosion"

Tab. 2

Changes in river channel volume in different areas of the North Branch of the Changjiang Estuary (unit: m3)"

Fig. 4

Temporal variation in the measured river discharge at Datong Station (a), and surface salinity at measuring stations Qinglonggang (b), Chongtou (c), Qingcaosha A (d), and Qingcaosha B (e), from February 15 to March 31. The red line represents 2007, and the green line represents 2025"

Fig. 5

Temporal variation of wind vectors at Chongming Dongtan meteorological station from March 8 to 31 in 2007 (a) and 2025 (b)"

Fig. 6

Distribution of tidal-period and vertically averaged salinity during spring tide (a, c, e) and neap tide (b, d, f) in February 2021 (a, b) and 2007 (c, d), as well as the distribution of differences in tidal-period and vertically averaged salinity between 2021 and 2007 (e, f)"

Fig. 7

Temporal variations of surface salinity at the output points of NB1 (a), NB2 (b), NB3 (c), and NB4 (d). The red line represents 2021; the black line represents 2007. The green dashed line indicates a salinity of 0.45‰"

Fig. 8

Temporal variations of surface salinity at the water intake of Dongfeng Xisha Reservoir (a), Taicang Reservoir (b), Chenhang Reservoir (c), and Qingcaosha Reservoir (d). The red line represents the year 2021 and the black line represents the year 2007. The green dashed line indicates the salinity threshold"

Fig. 9

Temporal variation of tidal level at Qinglonggang hydrometric station in February"

Tab. 3

Net water flux, net salt flux and water diversion ratio across the North Branch transect S1 during spring tide, middle tide after spring tide, neap tide, middle tide after neap tide and the whole tidal cycles in February 2007 and 2021"

Tab. 4

Tidal prism during spring tide, middle tide after spring tide, neap tide, middle tide after neap tide and the full tidal cycles across the transect S2 in the North Branch and transect S3 in the North Channel in February under the river regime conditions of 2007 and 2021 (unit: ×108m3)"

Fig. 10

Planar distribution of net unit-width water flux in the upper region of the North Branch during spring tide (a, c) and neap tide (b, d) in February of 2021 (a, b) and 2007 (c, d)"

Fig. 11

Planar distribution of net unit-width salt flux in the upper region of the North Branch during spring tide (a, c) and neap tide (b, d) in February of 2021 (a, b) and 2007 (c, d)"

Tab. 5

Net water flux, net salt flux and water diversion ratio across the North Channel transect S4 during spring tide, middle tide after spring tide, neap tide, middle tide after neap tide and the full tidal cycles in February 2007 and 2021"

Tab. 6

Net water flux and net salt flux across the transect S5 of Hengsha Channel during spring tide, middle tide after spring tide, neap tide, middle tide after neap tide and the full tidal cycles in February 2007 and 2021"